Microsoft Access를 사용하여 DataGridView를 업데이트 할 때 오류가 발생했습니다.

Question

Microsoft Access 2010을 사용하여 DataGridView에 레코드를 표시하려고합니다.하지만 문제는 button1을 클릭 할 때마다 "ConnectionString 속성이 초기화되지 않았습니다. "

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Data.OleDb; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows.Forms; 

namespace Attendance_Generation_System 
{ 
public partial class Take_attendance : Form 
{ 
    OleDbConnection conn = new OleDbConnection(); 
    public Take_attendance() 
    { 
     InitializeComponent(); 
    } 

    private void button1_Click(object sender, EventArgs e) 
    { 
     conn.ConnectionString=@"Provider = Microsoft.ACE.OLEDB.12.0; Data Source = F:\UNI WORK\7th Semester\Visual Programming\Database31.accdb; " + "User id = admin; " + "Password = "; ; 
     OleDbCommand cmd =new OleDbCommand("SELECT * FROM Attendancerecord"); 
     OleDbDataAdapter add = new OleDbDataAdapter(cmd); 
     DataTable dt = new DataTable(); 
     add.Fill(dt); 
     dataGridView1.DataSource=dt; 
     cmd.ExecuteNonQuery(); 
    } 
} 

}

Answer 1

오류가 당신에게 할당되지 않은 연결 문자열을 알려줍니다이 분명하다. 따라서 OleDbDataAdapter에 대한 연결 문자열을 할당해야합니다.

var connectionString = @"Provider = Microsoft.ACE.OLEDB.12.0; Data Source = F:\UNI WORK\7th Semester\Visual Programming\Database31.accdb; " + "User id = admin; " + "Password = "; 
using (var oledbCnn = new OleDbConnection(connectionString)) 
{ 
    oledbCnn.Open(); 
    var cmd = new OleDbCommand("SELECT * FROM Attendancerecord", oledbCnn); 
    OleDbDataAdapter add = new OleDbDataAdapter(cmd); 
    DataTable dt = new DataTable(); 
    add.Fill(dt); 
    dataGridView1.DataSource = dt; 
    oledbCnn.Close(); 
}